The present invention is directed to an optical sensor line of amorphous or polycrystalline photoelectric material having a plurality of sensor elements.
The photo currents of optical sensors rise approximately linearly with increasing luminous intensity, whereas the human eye logarithmically divides brightnesses into gray scales. As a result significantly more gray scales lie in the dark region in a prescribed photo-current interval than in the bright region.
The following problem is present when reading out optical scan lines with amorphous semiconductor sensors given high dynamics:
small signals that, for example, are smaller by a factor of 1000 than a maximum of the signals to be processed are submerged in switching signals and noise signals. A linear processing of the photo-currents in the dark region therefore yields a low gray scale resolution.
Previously, these problems were partially reduced with an optimum line management, with a pre-amplification with high levels and low output resistances and/or with a noise blanking.
In order to guarantee a digital data transmission of the gray scales having a high resolution in the dark region, a superfluously great plurality of gray scales results in the bright region when the gray scale division occurs linearly as was previously the standard approach.